bounce: Refactor __blk_queue_bounce to not use bi_io_vec

A bunch of what __blk_queue_bounce() was doing was problematic for the
immutable bvec work; this cleans that up and the code is quite a bit
smaller, too.

The __bio_for_each_segment() in copy_to_high_bio_irq() was changed
because that one's looping over the original bio, not the bounce bio -
a later patch renames __bio_for_each_segment() ->
bio_for_each_segment_all(), and documents that
bio_for_each_segment_all() is only for code that owns the bio.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>

diff --git a/mm/bounce.c b/mm/bounce.c
index 5f89017686025f9201d62486bde9dbf078dc4423..55f512af50c7ea6b35e7719fc31ad2111241615e 100644 (file)
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -101,7 +101,7 @@ static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
        struct bio_vec *tovec, *fromvec;
        int i;
 
-       __bio_for_each_segment(tovec, to, i, 0) {
+       bio_for_each_segment(tovec, to, i) {
                fromvec = from->bi_io_vec + i;
 
                /*
@@ -218,78 +218,43 @@ static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
                               mempool_t *pool, int force)
 {
-       struct page *page;
-       struct bio *bio = NULL;
-       int i, rw = bio_data_dir(*bio_orig);
+       struct bio *bio;
+       int rw = bio_data_dir(*bio_orig);
        struct bio_vec *to, *from;
+       unsigned i;
 
-       bio_for_each_segment(from, *bio_orig, i) {
-               page = from->bv_page;
+       bio_for_each_segment(from, *bio_orig, i)
+               if (page_to_pfn(from->bv_page) > queue_bounce_pfn(q))
+                       goto bounce;
 
-               /*
-                * is destination page below bounce pfn?
-                */
-               if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
-                       continue;
+       return;
+bounce:
+       bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
 
-               /*
-                * irk, bounce it
-                */
-               if (!bio) {
-                       unsigned int cnt = (*bio_orig)->bi_vcnt;
-
-                       bio = bio_alloc(GFP_NOIO, cnt);
-                       memset(bio->bi_io_vec, 0, cnt * sizeof(struct bio_vec));
-               }
-                       
+       bio_for_each_segment(to, bio, i) {
+               struct page *page = to->bv_page;
 
-               to = bio->bi_io_vec + i;
+               if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
+                       continue;
 
-               to->bv_page = mempool_alloc(pool, q->bounce_gfp);
-               to->bv_len = from->bv_len;
-               to->bv_offset = from->bv_offset;
                inc_zone_page_state(to->bv_page, NR_BOUNCE);
+               to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 
                if (rw == WRITE) {
                        char *vto, *vfrom;
 
-                       flush_dcache_page(from->bv_page);
+                       flush_dcache_page(page);
+
                        vto = page_address(to->bv_page) + to->bv_offset;
-                       vfrom = kmap(from->bv_page) + from->bv_offset;
+                       vfrom = kmap_atomic(page) + to->bv_offset;
                        memcpy(vto, vfrom, to->bv_len);
-                       kunmap(from->bv_page);
+                       kunmap_atomic(vfrom);
                }
        }
 
-       /*
-        * no pages bounced
-        */
-       if (!bio)
-               return;
-
        trace_block_bio_bounce(q, *bio_orig);
 
-       /*
-        * at least one page was bounced, fill in possible non-highmem
-        * pages
-        */
-       __bio_for_each_segment(from, *bio_orig, i, 0) {
-               to = bio_iovec_idx(bio, i);
-               if (!to->bv_page) {
-                       to->bv_page = from->bv_page;
-                       to->bv_len = from->bv_len;
-                       to->bv_offset = from->bv_offset;
-               }
-       }
-
-       bio->bi_bdev = (*bio_orig)->bi_bdev;
        bio->bi_flags |= (1 << BIO_BOUNCED);
-       bio->bi_sector = (*bio_orig)->bi_sector;
-       bio->bi_rw = (*bio_orig)->bi_rw;
-
-       bio->bi_vcnt = (*bio_orig)->bi_vcnt;
-       bio->bi_idx = (*bio_orig)->bi_idx;
-       bio->bi_size = (*bio_orig)->bi_size;
 
        if (pool == page_pool) {
                bio->bi_end_io = bounce_end_io_write;